Tiny Diamond Wires Could One Day Surge Through Computers

Below:

Next story in Science

Physicists have gotten a first look at the way electrons spin in
a tiny diamond wire, and taken another step to the next
generation of computing devices.

Computers use
electrons to send information — the 1s and 0s that make up
data bits are basically the presence or absence of current, which
is formed by moving electrons. Current generates heat, though,
and there are limits to how small you can make an electronic
circuit before it melts.

To make the next generation of computing devices, scientists have
been looking at spin, or " spintronics."
Spin in electrons is either up or down, and could store bits of
information the way that a flow of electrons being on or off
does. Such devices would emit less heat as they don't rely on
current, allowing for smaller circuits. [ Twisted
Physics: 7 Mind-Blowing Experiments ]

Some high-end hard drives already use spin effects to store
information. But to make useful spintronic computers scientists
must be able to see the spins and transmit them.

A team at Ohio State University was able to measure the
transmission of spin information in only a few electrons, using a
diamond wire only 4 micrometers long and 200 nanometers wide,
chilled to 4 degrees above absolute zero.

"The key result was that we measured the spin transport in this
diamond wire. We found that spin transport is efficient in
diamond wire," said study co-author Chris P. Hammel, a professor
of physics at Ohio State.

In the experiment, the scientists cooled the wire made of a tiny
artificial diamond stretched out into a thin wire shape — the
same stuff as in
a traditional engagement ring. They then turned on a magnetic
field and measured the spins of electrons in the wire with a
tiny cantilever. They found that the spin state was transmitted
down the wire, but unlike in an electric current, the electrons
stayed put. Instead the spin state traveled, not the actual
electrons, down the wire like a wave.

The diamond wasn't pure in the sense of being only carbon — it
was doped with a bit of nitrogen, in
order to give the electrons some room to "flip" their spins. They
chose diamond because it doesn't conduct electricity (encouraging
electrons to stay put) and doesn't hold heat. It's also hard, and
never corrodes. Artificial diamond has been made into nanometer
structures before, but it's never been used in quite this way.

Spin measurements have been done before, but those were made in
bigger volumes of material, and involved billions of electrons.
When scientists line up the spins to measure them, they need to
use big magnetic fields and can only align one electron in
10,000. To make the measurement, they look at an average of spin
states. Ordinarily 50 percent of the spins would be "up" and 50
percent would be down, but with a one in 10,000 difference among
billions of electrons, the average will go one way or the other —
up or down. It's like looking at a swing state's electoral votes
— even a small change in the average number of votes for one
party or the other will make the state "red" or "blue" if you
start with a 50-50 split.

"It's the 'big hammer' approach," Hammel said.

His team was able to align spins of a much smaller number of
particles and didn't need so strong a magnetic field.

Measuring
electron spins might seem esoteric. Understanding how to
measure the spins, though, does two things. One, it shows the way
toward making useful bits, as one can't have a working computer
without knowing whether the bits are spin-up or spin-down.
Second, the measurement reveals what happens in small volumes
where materials meet each other — in this case doped diamond wire
and the ordinary diamond.

"One of the thorniest questions is what happens at interface
between two materials," Hammel said. That's also the kind
of environment that exists in a computer chip.